In general, an acrylonitrile-butadiene-styrene-based resin (hereinafter, called ‘ABS’ resin) is widely used for electrical insulation, electronic parts, office machines, car parts and the like due to its relatively good properties such as impact resistance, mechanical strength, moldability, gloss and the like.
The ABS resin is prepared by a general emulsion polymerization method, for example, an emulsion polymerization method, which prepares diene-based rubber latex by emulsion polymerization, and then subjecting the latex to a graft reaction after adding an aromatic vinyl-based compound, a vinyl cyan-based compound and the like thereto to provide impact strength. Moreover, ABS thermoplastic resin can finally be prepared by mixing the graft copolymer prepared by the method with styrene-acrylonitrile-based resin (hereinafter, ‘SAN’ resin).
In recent efforts, in order to increase productivity and to improve production quality of this ABS resin, the proportion of rubbery polymer such as the diene-based rubber latex used for preparing the ABS graft copolymer is increasing. Because the content of the vinyl-based monomer is necessarily reduced when the content of this rubbery polymer is increased, the amount of grafted vinyl-based polymer will fall short. As a result, gloss is markedly reduced as incompletely grafted rubber polymers are fused during melt processing, and when the polymers stay at high temperature, there is a problem that thermal-depolymerization quickly progresses. However, there attempts to increase the rubber content face substantial technical challenges.
Moreover, because polymerization reaction should be generally performed for 30 hours or more to prepare the diene-based rubber latex and the like, there are problems of increased production time and production cost. Moreover, there is a problem that because polymerization conversion rate is quickly reduced at the polymerization conversion rate of 90% or higher when preparing the diene-based rubber latex, the polymerization conversion rate is not largely improved even if more reaction time is consumed. When conducting the polymerization under conditions of shorter reaction time and higher reaction temperature to overcome the problem, there are problems that particle diameter is decreased and reaction coagulation is increased. Thus, it was not easy to commercially prepare diene-based rubber latex having improved impact strength and ABS resin comprising the same.
Thus, in recent efforts, many companies have tried various methods for developing methods for preparing ABS resin to improve productivity, impact strength and the like in a process for preparing the ABS resin, but not changing the rubber content and not reducing other properties.